Telephone-exchange system



J A HALL TELEPHONE EXCHANGE SYSTEM Fi l od Oct. 1

Se t. 2 19214.

Patented Sept. 2, 1924.

UNITED STATES PATENT CFFICE.

JOHN A. HALL, OF BAYSIDE, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YGEK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed October 1, 1919.

T (ZZZ whom it may concern:

Be it known that I, JOHN A. I'IALL, a citizen of the United States, residing at Bayside, Long Island, in the county of Queens and State of New York, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to an improvement in telephone exchange systems of the type employing machine switching, and has particular reference to a system in which a special service feature is provided.

The invention is particularly applicable to a system such as disclosed in a patent to Samuel B. lVilliams, Jr. and Bert G. Dunham. issued October 12, 1920, No. 1,355,634, but the same may, of course, be used in other systems with equal facility.

In a patent to Bert G. Dunham issued October 12, 1920, No. 1,355,594, there is provided a system, also especially adaptable for use in connection with the above-mentioned patent, wherein subscribers may be given restricted service to a group of central oflice trunks. In accordance with this feature, switches employed in establishing a connection to a central ofiice trunk will fail to eX- tend the calling line to said trunk and will be returned to normal, whereupon the subscriber must again'dial for a connection to a private branch exchange or other operators position.

An object of this invention is to avoid the necessity of causing a restricted service subscriber to repeat the dialing operation to obtain a private branch exchange operators position when it is ascertained that a connection cannot be successfully established directly to a central oflice trunk.

In carrying out the above object, means are preferably provided whereby a restricted service line, when attempting to seize an idle central oflice trunk, will automatically be switched to a private branch exchange operators position. It is obvious that, in so doing, the loss of considerable time and the possibility of confusion on the part of the subscriber when he fails to secure a direct central oflice connection will be avoided.

Means are also provided to apprise the private branch exchange operator of the nature of the call, that is, to inform her before she communicates with the calling sub- Serial No. 327,733.

scriber that that subscriber has attempted to establish a call through the central oflice when that privilege is, by the nature of the service for which he has contracted, denied him.

The inventive idea involved is capable of receiving a variety of expressions one of which, for the purpose of illustrating the invention, is shown in the accompanying drawing; but it is to be expressly understood that said drawing is employed merely for the purpose of facilitating the descrip tion of the invention as a whole and not to define the limits thereof, reference being had to the appended claims for this purpose.

The drawing illustrates diagrammatically the circuits employed in carrying out the invention.

It is believed that the invention will be best understood from a detailed description of the operation. Upon the removal of the receiver at substation A, in initiating a call, line relay 200 of the line switch B is energized over a circuit from grounded battery, winding of relay 200, back contact and in nermost lower armature of cut-off relay 201, substation apparatus, upper armature and back contact of relay 201 to ground. The marginal stepping magnet 202 is then energized over a circuit from grounded battery, winding of said magnet, armature and back contact thereof, front contact and armature of line relay 200 and lowermost brush 208 to ground at the normal terminal thereof, whereupon the brushes of the switch will be stepped to the second set of terminals, the trunks of which lead to one of the first selector switches. Should the selector switch connected to the first test terminal be busy, brush 203 of the line switch B engaging said terminal will be grounded at the back contact of the line relay of the line switch connected to said selector switch, and a circuit will be found for stepping magnet 202 extending from grounded battery, winding of said magnet, armature and back contact thereof,front contact and armature of relay 200, brush 203, armature and back contact of the line relay of said line switch to ground. Magnet 202 being self-interrupting, will again step the brushes of the line switch over the terminal bank until an idle trunk is found, whereupon a circuit is established from grounded battery, winding of magnet 202, back contact and armature the trunk test busy to all other line switches,

Line relay 309 of the selector switch will energize immediately upon energization of relay 307, due to'the circuit extendin from grounded battery, right winding 0 relay 309, armature and front contact of relay 307 to ground, and the circuit for relay 309 will be maintained from grounded battery, right winding of relay 309, lower alternate contact of cut-off relay 310, lower side of the subscribers line, substation apparatus, upper side of subscribers line, upper alternate contact of relay 310, left winding of relay 309, brush 311 and coil 312 to ground. First s-low-to-release relay 305 is then energized by a circuit extending from grounded battery, winding of relay 305, front contact and armature of line relay 309 to ground. A dial tone is furnished by coil 312 and the subscriber may now operate his sending de vice to select a particular group of trunks terminating in the bank of the selector switch 0, in accordance with the operation as set forth in the patent to Williams and Dunham previously referred to and to which reference is made for a complete understanding of the operation of said selector and other switching means not illustrated or described herein, for establishing a connection.

Should the subscriber, after initiating a call, hang up his receiver before an idle trunk leading to the selector switch has been seized, it will be apparent that the line switch will continue to hunt for the idle trunk and upon finding the same, cut-off relay 201 will be energized as previously described. Relay 307 being in series with relay 201 also energizes, and at its front contact, closes a circuit for line relay 309 extending from grounded battery, right Winding of line relay 309, armature and front contact of relay 307 to ground, and relay 309, in attracting its armature, energizes slow-torelease relay 305, thus grounding conductor 30 1, leading from cut-oif relay 201 at the left armature of relay 305, instead of at the back contact and right armature of relay 301 and thereby shunting relay 307. Release of this relay deenergizes the line relay 309 since the line circuit has been broken by replacing the receiver, and armature of relay 309 closes the circuit of stepping magnet 313 extending from grounded battery, winding of said magnet, winding of relay 301, right armature of relay 305, back contact and outermost lower armature of relay 310, back contact and armature of relay 309 to ground, and the brushes are stepped onto the second set of terminals. Group relay 320 is then energized over a circuit extending fromi grounded battery, winding of relay 320, brush 303, back contact and inner right armature of test relay 303,,back contact and right armature of slow-to-release relay 301 to ground. The right armature of group relay 320 puts ground on the set of test terminals associated therewith and test relay 303 is consequently energized by the circuit extending from grounded battery, right winding of relay 303, brush 316, front contact and right armature of relay 320 to ground. Energization of relay 303 closes the circuit for stepping magnet 313 from grounded battery, winding of magnet 313,

armature and back contact thereof, front 1 contact and outer left armature of relay 303 and back contact and left armature of relay 305 to ground, the latter relay haying become deenergized upon the release of line relay 309. The brushes are now stepped to the next set of terminals and this-action takes place each time the brush 316 engages one of the terminals which finds ground "at the right armature of group relay 320. When engaging the test terminals of different groups of trunks in the selector bank, brush 316 finds ground for test relay 303 at the back contacts and armatures of the respective group relays 314:, 315 and 321, and stepping magnet 313 continues to operate until the last set of terminals is reached. WVhen this occurs a circuit is closed for test relay 303 extending from grounded battery, right winding of said relay, brush 316, right alternate contact of relay 305, back contact and lowermost armature of relay 310, and

back contact and armature of relay 309 to ground, relays 305 and 309 having released when the calling subscriber replaced his receiver. A circuit is now established for magnet 313 extending through its winding,

armature and back contact, front contactand outer left armaturecf relay 303 to ground at the left alternate contact of relay 305. Magnet 313 steps the brushes of the switch from the last to the first or normal set of terminals whereupon the parts will again be .in normal position.

Upon the shunting of relay 307, relays 309 and 305 will release and the circuit for cutoff relay 201 of line switch B will be broken at the left armature of relay 305. Stepping magnet 202 is then energized over a circuit extending from grounded battery, winding of magnet 202, armature and back contact thereof, lowermost armature and back contact of relay 201, and brush 205' to ground at the armature and back contact of line relay 200. Stepping magnet 202 continues to operate until the brushes thereof engage the normal terminals, whereupon the operating circuit of said magnet will be broken and the switch will come to rest.

Let it now be assumed that the service of substation A is restricted, in which event a call initiated therefrom to the central office will be routed through a private branch exchange operators position. In order to accomplish this purpose, a conductor 207 is employed to connect the middle lower armature of cut-off relay 201 of the line switch with brush 206, so that if an at tempt is made to call the central office from sub-station A, energization of cutoff relay 201 will apply ground to said brush. In accordance with the practice set forth in the previously mentioned joint patent, the brushes of switch C will be stepped from their normal terminals and upon engaging the second row of terminals, a circuit is established for group relay 320 extending from grounded battery, winding of said relay, brush 308, back contact and inner right armature of test relay 303, and right alternate contact of relay 301, to ground. telay 320 energizes and locks up through its winding, inner left armature and front contact, the back contacts and left armatures of relays 314 and 315, back contact and inner left armature of relay 321, and left armature and alternate contact of relay 305, to ground, said relay having become energized upon the seizure of the selector switch C. The previously mentioned ground applied to brush 206 is now extended to conductor 323, front contact and middle left armature of relay 320 and winding of group relay 321, to grounded battery. Relay 321 energizes and locks up through its winding, front contact and inner left armature and the left armature and alternate contact of relay 305, to ground.

Upon the energization of relay 321, a circuit is established for relay 32 1 extending from grounded battery, winding of said relay, outer left armature and front contact of relay 321, outermost left armature and front contact of relay 320, conductor 323, brush 206, conductor 207, and middle lower armature and front contact of relay 201, to ground. Relay 324C energizes in this circuit and locks up through its upper armature and front contact, contact and armature of relay 325, front contact and inner left armature of relay 321, left armature and alternate contact of relay 305, to ground. It will be recalled that the locking circuit for relay 320 extends through the back contact and inner left armature of relay 321 so that upon the energization of the latter relay the looking circuit for relay 320 will be opened and said relay will release. The deenergization of relay 320 will apply ground through its right armature to the terminals assigned to the central office trunks and thus bar the selector switch C from seizing any one of them. The energization of relay 321 will remove ground from its right armature and conse quently from the group of terminals individual to the private branch exchange operatorss trunks, thus permitting the selector switch to seize an idle one when the brushes of the switch pass thereover.

Relay 324, when energized as previously described, connects an interri'lpter to the talking circuit so that when a trunk to the private branch operator is seized by a restricted service subscriber, and relay 310 energized in the ordinary manner, line relay 327 located at the operators position will be intermittently energized. By attracting its left armature, a circuit is established for relay 328 and this relay being slow to release, will maintain its arn'iature attracted during the vibration of the armatures of relay 327. Energization of relay 328 applies ground to contact 329 which affords a busy test for the seized trunk. The vibration of the right armature of relay 327 in response to the intermittent energization thereof will cause a flashing of the lamp 330 at the operators position and thus inform her of the call requiring attention. By causing the lamp to flash intermittently the operator will understand that a restricted service subscriber is attempting to secure a. direct connection to a central office trunk. In the ordinary operation, where a subscriber calls the private branch operator, it is obvious that the interrupter 326 will not be included in the circuit and therefor the lamp 330 will burn steadily. The operator now establishes a connection to the calling line in the ordinary manner by inserting the plug into the jack 331. This causes the energization of cut-off relay 332 which permanently opens the circuit for line relay 327 and also transfers a busy test from relay 328 to the outermost armature and front contact of relay 332. By the insertion of the plug into the jack 331 there is caused an increased flow of current in the line which will energize relay 325. By attracting its armature this relay opens the locking circuit for relay 324 and said relay then releases. Conversation may now proceed between'the rivate branch exchange operator and the calling subscriber in the ordinary manner. The operator may release the connection by removing the plug from jack 331 as usual and at the termination of the call the switches B and C are restored in the manner described in the previously mentioned joint patent.

What is claimed is:

1. In telephone system, telephone lines, switches for extending said lines, groups of trunks, senders for said lines, switching means for further. extending said lines to a trunk in any one of said groups, and means associated with certain calling lines, whereby said switching means is automatically operated, when a certain trunk group is dialed,

to extend the calling line to an idle trunk in a differentgroup.

2. In a telephone system, a calling subscribers line, groups of trunks, switching means for extending said line to a trunk in any one 01 said groups, means controlled by the calling subscriber for operating said switching means, and means independent of said controlling means for operating said switching means to extend said line to any one o1 a plurality of trunks in a non-equivalent group 3. In a telephone system, a calling subscribers line, a switch for extending said me, a terminal bank, a plurality of trunks terminating in said bank and arranged in groups, an operators position assigned to one of said groups, a second switch under the control of the calling subscribers line for selecting any one of said groups of trunks, and means at the first switch and independent of said calling subscribefis line for causing said second switch to select the group of trunks assigned to said operators position.

4:. In a telephone system, a calling su'bscribers line, a switch for extending said 11116., a terminal bank, groups of trunks terminatrng 111 said bank, certain of the terminals of the bank being allotted for group selection, a single movement switch for connecting said subscribers line with a trunk in any one of said groups, means under the control of said subscribers line for operating said single movement switch, and means at the first named switch operable to cause said single movement switch to select a group of trunks other than that selected by the means under the control of the calling subscribers line.

5. In aftelephone system, telephone lines, senders therefor, groups of trunks, automatic switching mechanism wherein said trunks terminate, indicating means for the trunks of one of said groups, means for operating the same in one manner when a trunk of said latter group is selected, and means for causing the selection of the same itrunk group and for operating the indicating means of the seized. trunk in another manner when certain of said lines attempt to select a clitterent trunk group. v

In witness whereof, I hereunto subscribe my name this 19th day of "September A. 1)., 1919.

JOHN A. HALL. 

